y'=2x-25/x^2
2x-25/x^2=0
(2x^3-25)/x^2=0
x=(25/2)^(1/3)
y''=2+50/x^3
y((25/2)^(1/3))=(25/2)^(2/3)+25* (2/25)^(1/3)=(25/2)^(2/3)+1250^(1/3)